With continuous development of mobile communications technologies, a requirement and a service type oriented to a mobile communication service continuously increase. One service is locating a mobile terminal (MT). Locating a mobile terminal MT is extracting, by means of information exchange between the MT and a base station (BS), characteristic information that can be used for locating, so as to estimate an MT location.
There are multiple types of currently popular locating technologies. From a perspective of only a wireless cellular locating technology, there are an advanced global navigation satellite system (A-GNSS) locating technology, an observed time difference of arrival (OTDOA) locating technology, an enhanced cell identification (E-CID) locating method, an uplink-time difference of arrival (UTDOA) locating technology, a radio frequency pattern matching (RFPM) locating technology, and the like. According to a difference in a locating parameter, the locating technology may be divided into an angle of arrival measurement technology (AOA), a time of arrival (TOA) locating technology, a time difference of arrival (TDOA) locating technology, and the like. For example, the OTDOA and the UTDOA locating technologies are derived based on a TDOA technology principle. TDOA is obtained by means of calculation by using TOA as a reference quantity. Therefore, in the wireless cellular locating technology, the TOA is used as a base quantity, and measuring and obtaining the TOA are quite important for developing and applying a locating technology.
In a locating method, TOA estimation is generally obtaining a propagation delay value by detecting a first arrival path (FAP), that is, searching for the first arrival path is a basis for obtaining the TOA. When clocks of a transmitter and of a receiver are synchronized, generally, a commonly used mechanism for detecting a received signal is that the receiver receives a reference signal sent by the transmitter, calculates a time domain related convolution value of the reference signal to obtain a power spectrum that is corresponding to a delay value and that is of the reference signal in a time domain, and searches for a corresponding delay value when power is greater than or equal to a related spectrum threshold for the first time. The delay value is the time of arrival TOA, and a distance between the receiver and the transmitter can be obtained by means of calculation according to the TOA.
However, an inventor finds through research that in a conventional technology, in a TOA-based locating method, a method for obtaining TOA by searching for a first arrival path FAP has at least the following problem: In the conventional technology, the foregoing related spectrum threshold is a constant value, that is, is not changed without reason after being set. This manner is suitable only for an environment with a relatively good channel environment. When the channel environment is relatively poor and interference is relatively strong, a probability of incorrectly determining a first arrival path increases due to noise interference. Therefore, in the conventional technology, a channel environment adaptability of a manner of obtaining TOA by searching for a first arrival path FAP based on a constant threshold is relatively poor, thereby decreasing ranging accuracy.